Commutator assemblies

ABSTRACT

The invention concerns a commutator assembly comprising a commutator support in which a plurality of commutator segments having an outer working surface are mounted. A preformed insulating shield is positioned at least partly over the commutator support and is keyed into the commutator segments below the outer working surface thereof. The preformed insulating shield is of hollow cylindrical shape open at one end, and closed at the other end by a plate having an axial hole therein.

United States Patent 1191 Etter COMMUTATOR ASSEMBLIES Marcel'Etter, Bryanston, South Africa Marc Etter (Proprietary) Limited, Bryanston', Transvaal Province, South Africa Filed: Oct. 4, 1972 Appl. No: 295,071

Inventor:

Assignee:

[30] Foreign Application Priority Data Oct 25, 1971 South Africa 71/7115 us. c1. 310/236 1111. c1. H02k 13/04 Field of Search... 310/233, 235, 236, 238, 239,

References Cited UNITED STATES PATENTS 3 1950 Wright 310/236 1451 Feb. 19,1974

Mueller 310/236 2,468,844 5/1949 Sutherland 3,141,984' 7/1964 Rubin-Medina 310/236 3,036,023 5/1962 Rogers 310/236 2,899,574 8/1959 .Iungk 310/236 Primary ExaminerR. Skudy Attorney, Agent, or Firm--Ladas, Parry, Von Gehr, Goldsmith & Deschamps [5 7 ABSTRACT .axial hole therein.

6 Claims, 1 Drawing Figure COMMUTATOR ASSEMBLIES This invention relates to improvements in commutator assemblies.

The present invention provides a commutator assembly comprising a'commutator support in which a plurality of commutator segments having an outer working surface are mounted, and a preformed insulating shield positioned at least partlyover the commutator support and keyed into the commutator segments below the outer working surface thereof.

The commutator support may comprise the combination of a commutator shell and commutator cap fitted together. The shell and cap between them may define an undercut channel in which the commutator segments are held. Standard insulation may be provided around the channel between the segments and the shell and cap. The insulating shield can conveniently fit over the commutator cap.

The commutator segments may extend partly over the commutator cap. The segments may have a groove formed in their underside adjacent to the cap, which groove can have a lip. The insulating shield can be shaped (e.g., the endcan be splayed) so that it may fit into this lipped groove. The end of the shield which fits into the lipped groove can be sufficiently flexible to press against the sides of the groove after being forced under the lip. Conveniently, an elastic ring (e.g., of an elastomeric substance or a spring) may be positioned on the commutator cap to force the end of the shield against the sides of the groove when the shield is in the desired position.

The shield may be of hollow substantially cylindrical shape open at the one end adapted to fit over the cap and closed at the other end by a plate having an axial hole therein. As mentioned above, the open end may be splayed outwardly. If the commutator cap has an inwardly-directed shoulder, the shield may have an inwardly directed lip around the axial hole in the plate and adapted to pass over the shoulder. The length of the lip may be such that it is possible to apply leverage under the lip so that the shield may be removed and reused when the commutator assembly is worn out.

If desired, an annular disc can be positioned under the lip of the shield before fitting the shield over the shoulder of the cap. The disc may contain jacking screws to assist in removal of the shield. On screwing the jacking screws in, the disc is forced outwardly and so can pull the shield off the commutator cap.

The shield may be of any suitable electrical insulating material which can be preformed to a desired shape, e.g., by moulding or machining. Polytetra fluoroeth-- ylene (P.T.F.E.) may for example be used.

The invention is illustrated by reference to the accompanying drawing which shows a commutator assembly according to the invention in elevation with the upper half sectioned.

in this FIGURE, a commutator assembly shown generally at comprises a commutator shell 12 and commutator cap 14 held in place by nut 15. The shell 12 and cap 14 between them define an undercut channel 16. Held in the channel 16 are a plurality of commutator segments 18 having an outer working surface 20 adapted to be contacted by carbon brushes (not shown). Insulation strips 22, 24, 26 are provided between the segments 18 and the cap 14 and shell 12.

The cap 14 has a shoulder 28 and body 30. A polytetra fluoroethylene insulating shield 32 of hollow cylindrical shape with one end closed by annular plate 34 having a lip 36 fits over the shoulder 28. An annular disc 38 with jacking screws 40 is positioned between the rim 36 and the body 30. End 42 of the shield 32 is splayed slightly outwardly to press upwardly against the surface of a groove 44 having an overhanging lip 46 and cut out of the commutator segments 18. An elastomeric ring 48 presses the end 42 outwardly. The commutator assembly is mounted fast on a shaft 48.

Carbon from the brushes, which passes onto the shield 20 is kept away from the cap 14 so that a discharge or flashover can be avoided or reduced.

1 claim:

l. A commutator assemblycomprising a commutator support in which a plurality of commutator segments cylindrical shape open at one end and closed at the other end by a plate having an axial hole therein.

2. A commutator assembly according to claim 1 wherein the commutator support comprises a commutator shell and commutator cap fitted together, the commutator cap having an inwardly-directed shoulder, and the preformed insulating shield having an inwardlydirected lip, adapted to pass over the shoulder.

3. A commutator assembly according to claim 2,

wherein an annular disc containing jacking screws is positioned between the lip and the commutator cap. 4. A commutator assembly according to claim 2, wherein the preformed insulating shield is keyed into a groovev cut in the underside of the commutator segments adjacent to the commutator cap, the preformed insulating shield having a corresponding rib on its outer surface.

5. A commutator assembly according to claim 4, wherein the rib is forced into the groove by means of an elastic ring positioned between the commutator cap and the inside of the preformed insulating shield.

6. in a commutator assembly comprising a commutator support in which a plurality of commutator segments having an outer working surface are mounted, an insulating shield comprising a hollow cylinder of electrically insulating material open at one end and closed at the other end by a plate having an axial hole therein with an inwardly-directed lip around the axial hole, the shield being of a predetermined size and shape to fit over the commutator support and to be keyed into the commutator segments below the outer working surface thereof. 

1. A commutator assembly comprising a commutator support in which a plurality of commutator segments having an outer working surface are mounted, and a preformed insulating shield positioned at least partly over the commutator support and keyed into the commutator segments below the outer workings surface thereof, the preformed insulating shield being of hollow cylindrical shape open at one end and closed at the other end by a plate having an axial hole therein.
 2. A commutator assembly according to claim 1 wherein the commutator support comprises a commutator shell and commutator cap fitted together, the commutator cap having an inwardly-directed shoulder, and the preformed insulating shield having an inwardly-directed lip, adapted to pass over the shoulder.
 3. A commutator assembly according to claim 2, wherein an annular disc containing jacking screws is positioned between the lip and the commutator cap.
 4. A commutator assembly according to claim 2, wherein the preformed insulating shield is keyed into a groove cut in the underside of the commutator segments adjacent to the commutator cap, the preformed insulating shield having a corresponding rib on its outer surface.
 5. A commutator assembly according to claim 4, wherein the rib is forced into the groove by means of an elastic ring positioned between the commutator cap and the inside of the preformed insulating shield.
 6. In a commutator assembly comprising a commutator support in which a plurality of commutator segments having an outer working surface are mounted, an insulating shield comprising a hollow cylinder of electrically insulating material open at one end and closed at the other end by a plate having an axial hole therein with an inwardly-directed lip around the axial hole, the shield being of a predetermined size and shape to fit over the commutator support and to be keyed into the commutator segments below the outer working surface thereof. 